1. Field of the Invention
The present invention relates to an optical information recording apparatus, an optical information reproducing apparatus and an optical information recording medium and can be applied to e.g., an optical disk for recording a video signal, etc., its recording apparatus and reproducing apparatus.
According to the present invention, timing of the irradiation of a laser beam and a light amount of the laser beam are controlled, and subdata required to process reproduced data obtained by judging a reproduced signal with a threshold value as a reference is recorded by an amplitude value of the reproduced signal with respect to the reproduced data so that an illegal copy can be effectively avoided.
2. Background of the Invention
For example, in a compact disk as a conventionally known optical information recording medium, data to be recorded is subjected to an eight-to-fourteen modulation (EFM) so that a series of pits is formed in a period from 3T to 11T with respect to a predetermined basic period T. Thus, audio data, etc. are recorded.
In a compact disk player for reproducing the above compact disk, a return light is received by irradiating the laser beam onto the compact disk so that a reproduced signal having a signal level changed in accordance with a light amount of this return light is obtained. This reproduced signal is changed to be two-valued at a predetermined slice level so that a binary signal is generated. Further, a PLL circuit is driven by this binary signal so that a reproducing clock is generated. The binary signal is sequentially latched by this reproducing clock so that reproduced data varying in a period from 3T to 11T in response to the pit series formed on the compact disk is generated.
The compact disk player is arranged such that the reproduced data generated in this way is decoded by data processing corresponding to that used at the recording time, and audio data, et. recorded on the compact disk are reproduced.
In a transmission system for transmitting the audio data, etc. through the recording medium of optical information in this way, a copy preventing system as shown in e.g., FIG. 1 or 2 is proposed to effectively avoid an illegal copy.
Specifically, in a copy preventing system 1 shown in FIG. 1, data D1 to be recorded is scramble-processed by a master key KM in an encoder 3 on a disk manufacture side 2 and the scramble-processed data is recorded on an optical disk 5. Further, for example, reproduced data reproduced from the optical disk 5 is descrambled by the master key KM common to the disk manufacture side 2 in a decoder 7 of a reproducing apparatus 6, and the descrambled-processed data is processed by a decoder 8 of a MPEG, etc. Thus, the copy preventing system 1 enciphers the data D1 to be recorded by using the master key KM common to the reproducing side determined in advance so that the illegal copy is prevented.
A copy preventing system 10 shown in FIG. 2 enciphers data D1 by a master key KM, a disk key KD inherent to an optical disk 11, and a title key KT inherent to each of literary work. Namely, a disk manufacture side 12 scramble-processes the disk key KD by the master key KM in an encoder 13 and records this scramble-processed disk key KD on the optical disk 11. Further, in an encoder 14, the title key KT is scramble-processed by the scramble-processed disk key KD and the scramble-processed title key KT is recorded on the optical disk 11.
Further, the disk manufacture side 12 scramble-processes the data D1 to be recorded by the scramble-processed title key KT in an encoder 15, and then records the data on the optical disk 11. Thus, the disk manufacture side 12 scramble-processes the data D1 in multiple with the master key KM as a reference and records the data D1 on the optical disk 11.
In contrast to this, a reproducing apparatus 16 descramble-processes the scramble-processed disk key KD by the master key KM and decodes the disk key KD in a decoder 17. Further, in a decoder 18, the scramble-processed title key KT is descramble-processed by the disk key KD. In a subsequent decoder 19, the data D1 is descramble-processed by this disk key KD.
Thus, the copy preventing system 10 is arranged such that an illegal copy is prevented in consideration of the stands of a disk manufacturer and a maker of literary works.
It is considered that there are two kinds of the illegal copy. One of the illegal copies is made by a method in which the master key, is decrypted and an optical disk is manufactured such that the optical disk can be reproduced by the reproducing apparatus on the basis of results of the decryption even when the optical disk is a pirated disk. The remaining illegal copy is made by a method for physically copying a pit shape formed on a normal optical disk.
In the copy preventing system using the master key, it is possible to cope with the former illegal action by making the decryption of the master key, difficult. However, when the master key is once decrypted, there is a defect in that no pirated disk can be excluded. It is also impossible to cope with the latter illegal copy.